I often hear this from nature activists and groups like that. Yes, mining coins (and by that, making transactions possible) does take a lot of energy. Yes, it was better if this didn't took as much energy as it does now, but you know this "difficulty" makes the coin gain value.
Now, the current system of banks. I think they use even more energy for ordinary transactions of money..
but coin is heavier than paper money, and feel free to convince me money transaction costs more energy than mining coins.
Sure. Let's factor in everyone that is employed by the banking system - the energy cost of paying them and putting them in an office and making them productive workers and their car rides to and from work and their A/C and computers and all the rest - just as a start....